Repair of a big hole in aluminum keel

swimmin' for shore · #1 August 22nd, 2005, 06:51 AM

The title says it all. I have 1/2" crack. As much as 3/4" wide in some places. It runs about a foot and a half long, right up around the bow.

Riveted construction aluminum boat, but crack isn't crossing any rivets.

Weld it, or is that too expensive? Can I fill it with anything? I have some epoxy putty, but I was concerned about it etching into the aluminum.

Thoughts?

swimmin' for shore · #2 August 22nd, 2005, 06:54 AM

Something about the whole first sentence of that just doesn't sound quite right. Try to control yourselves.

Captn Dave · #3 August 22nd, 2005, 08:17 AM

I would do what is called a doubler repair.

First you would need to find a piece of marine grade aluminum that's a little thicker or close to the thickness of the boat. Try a small aircraft repair facility if you can't find any.

Stop drill the crack on each end with a .040 drill. Then cut a piece of aluminum about 4" wide and and 4 inches longer than the crack. Install the doubler inside with 3M 5200 sealant and two rows of pop rivets on each side of the crack. Coat the rivets with 3M before installing.

JB · #4 August 22nd, 2005, 08:20 AM

Check with Home Depot for aluminum brazing rod that can be used with a propane or MAPP gas torch.

You can patch it yourself.

After the repair I suggest a KeelGard.

Good luck.

swimmin' for shore · #5 August 22nd, 2005, 08:39 AM

Thanks to both of you. I have the alumaweld rod. It works fantastically for small holes, but this is a pretty wide one. Kind of a pain to braze that much without warping everything. This is a 64 Mirrorcraft, and it is really built well, but I still warped a small spot on the transom when I brazed it yesterday.

BF · #6 August 22nd, 2005, 01:59 PM

I'd take it to a welder who routinely does boats. A guy who does a lot of props would be OK too.. basically someone who does boat stuff... NOT the trailer hitch shop.

When I bought an alumium beater boat in, with several cracks, he cut a bunch of reinforcing patches and welded them on for ~$100. He knew all about the different aluminum alloys and which type of patch material to use etc. Boat already had a big reinforcing plate about 2' long welded on the front part of the bow (where you'd drag it up on rocks)... I didn't have to re-patch that.

A couple seasons later and haven't had any problems.